1. Field of the Invention
The present invention relates to railroad dump cars. In particular, the present invention is a hydraulically powered system for operating the dumping mechanism of the dump car.
2. Description of the Prior Art
Since about 1920, the railroad industry has built what is known as a side dump rail car. The car consists of a main car frame and a dump body pivotally connected to the car frame so that it is capable of tilting to a 45.degree. angle, on either side of center. As the dump body tilts, a side door also drops. This design is well suited for unloading bulk commodities and large, difficult to handle material.
The overall design of side dump rail cars has not changed materially in 60 years. Power to lift either side of the dump body comes from a pair of approximately 26" bore telescopic air cylinders mounted directly under each side of the dump body (four cylinders in all per car). By operating a control lever on one side of the car, air from the train's auxiliary air system is directed to the air cylinders on the same side of the car as the lever. This causes dumping of the contents of the car on the opposite side of the car from the operator.
The prior art air operated dump car systems have several significant disadvantages. First, water vapor in the train's auxiliary air system can condense in the rail car components and piping and freeze during cold winter months in northern climates. This prevents operation of the air operated dumping system.
Second, the compressibility of the air poses serious safety hazards. For example, it can create a condition where the car dumping cannot be stopped due to the residual forces of the compressed air, even though the control lever has been released. This can cause derailing of the dump car.
Third, the large bore air cylinders required to pivot the dump body cannot be made really tight. Piston bypass leakage allows rapid settling of the car in midposition. This also poses a significant safety hazard.
Fourth, the prior art systems are expensive to build and maintain. The large bore air cylinders are specially made, difficult to obtain, and expensive. In addition, due to the large size and weight of the air cylinders, replacement of a worn-out or defective air cylinder with a new air cylinder is time-consuming and expensive.
Other types of railroad dump cars, such as bottom slide gate cars, also use air cylinders to move a movable dumping mechanism to thereby unload the contents of the dump car. Like the side dump rail car, these other air operated dump cars suffer from serious performance, safety, and cost disadvantages associated with the air cylinder system.